Accessory Structures in West Allis, WI: What Residents Actually Need to Know

If you live in West Allis or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. West Allis has 2 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

Shed & Carport Rules

West Allis limits a detached shed ('Other Accessory Building') to 300 square feet and 15 feet of height, set back 60 feet from the front lot line and 3 feet from the side and rear lines.

Key details: Max size: 300 sq. ft.. Max height: 15 feet. Front setback: 60 feet minimum. Side/rear setback: 3 feet minimum. Over 150 sq. ft.: must match house design.

Violating Chapter 19's accessory building standards carries a forfeiture of $25 to $500 per offense plus prosecution costs, with each day of continued violation counted separately under § 19.12.

ADU Rules

West Allis allows one accessory dwelling unit per lot as a limited accessory use in most residential and several commercial districts, defined as any dwelling unit besides the principal one.

Key details: Limit: 1 accessory dwelling unit per lot. Eligible districts: RA-1-3, RB, RC, C-2-4. Use classification: Limited accessory use. Definition: Any dwelling unit besides principal unit.

A second accessory dwelling unit on the same lot, or an ADU built in a district where the use isn't listed, such as C-1, I-1, I-2, P or SF, exceeds what the accessory-use table allows.

The Bottom Line

West Allis's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming West Allis is broadly strict or permissive.

All of the above reflects West Allis's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.